The present invention relates to a printing device for printing characters/symbols on a tape-shaped recoding medium, and more specifically, to a printing device provided with a tape cut mechanism for cutting the tape-shaped recording medium.
The Applicant has disclosed such a printing device as described above in the European Patent Application EP 0429873A2, U.S. Pat. No. 4,927,278.
Further, conventionally, there has been known a printing device for printing characters/symbols on a tape-shaped recording medium provided with a tape cutting mechanism on the downstream side along the tap feed direction. The Applicant has disclosed such a tape cutting mechanism in the U.S. Pat. No. 5,066,152. In such a printing device, the printed tape-shaped recording medium is fed by a predetermined amount so that an appropriate rear margin is added, and then the tape-shaped recording medium is manually or automatically cut by the cutting mechanism. In such a printing device, however, it has been impossible to cut the tape to have a desired top margin, i.e., a blank portion ahead of the portion where the characters/symbols are printed. The top margin is to be set by cutting the tape with, for example, scissors.
In the tape print device provided with the tape cut mechanism, there has been desired that the tape-shaped recording medium is automatically cut so as to have a desired top margin.
In the meantime, it is preferable that a tape feed motor is driven at relatively high speed for high-speed printing operation. Generally, a pulse motor is used as the tape feed motor. In order for the pulse motor to be driven without step-out, the motor is applied with a pulse having a so-called self-start frequency when the motor starts rotating. Further, in order to drive the motor at relatively high speed, the motor is applied with a pulse having frequency greater than the self-start frequency. When the motor is driven by the pulse having the frequency greater than the self-start frequency, the following control becomes necessary:
(1) when the motor is stopped, the frequency of the pulse applied to the motor is gradually decreased (slow-down); and
(2) when the motor starts rotating, pulse having the self-start frequency is applied to the motor, and thereafter, the frequency of the pulse is gradually increased (slow-up).
In order to cut the printed tape-shaped recording medium so as to have a top margin with the tape cutting mechanism, feeding and printing of the tape should be temporarily stopped during printing operation. In this case, however, the tape is fed without being printed and thus a printed character is divided due to the slow-down, i.e., a gradual decreasing of the rotational speed of the tape feed motor for ceasing thereof, and due to the slow-up, i.e., a gradual increasing of the rotational speed of the motor for restarting thereof. It should be noted that, during the slow-up and slow-down of the motor, a period for removing the thermal transfer ribbon from the recording medium becomes long relative to the case when the motor is normally rotated. Therefore, during the slow-up and slow-down of the motor, the temperature of the thermal head is lowered. With this condition, transferring of the ink form the thermal ribbon to the recording medium becomes incomplete, which loweres the quality of the printed characters/symbols and the like. In order to avoid this problem, printing operation is inhibited during the slow-down and slow-up of the motor.
For avoiding the above described division of the printed characters/symbols, the tape feed motor must be driven at a relatively low speed. In this case, however, a problem arises in that since the tape feed motor is driven at the low speed, printing efficiency becomes greatly lowered even if the top margin is not required or a large number of characters/symbols are printed.
Therefore, it may contemplated that the tape feed motor is driven at relatively high speed, the motor and print processing are temporarily stopped when the tape is cut so as that a top margin is remained, and then, in order to prevent a printed character/symbol from being divided, the tape is fed in a reverse direction by a length corresponding to the amount caused by the slow-down and the slow-up of the motor after the tape has been cut. In this case, however, it is necessary to modify the print mechanism so that the tape can be reversely fed, thus a problem arises in that the print mechanism must be improved for this purpose, and as a result the print mechanism becomes complex.